Well I started off this week with the goal of making another sky brightness measurement, but the weather has just not been cooperating. We can see a few stars but way to many clouds. We have also been looking into booking a visit to Joshua Tree and Pioneertown to get some dark sky observing, but again the weather has not been great for that either. But just by chance, the cold weather created one opportunity to see the ring around the moon that occurs when light refracts off the ice crystals high up in the atmosphere.
I remember seeing the calculations one time that described how the ring would be formed at 22 degrees radius around the moon. I probably couldn't do that calculation now, but I did measure the diameter of the ring in the uncropped image and found it to be 21 degrees radius when I measured to the middle of the ring. I can't remember for sure but optical theory probably says you should measure from the outermost part of the ring, which if that is the case, then my measurement would be 22 degrees also.
This image was taken about 6:11 PM in the evening and when I first noticed it in the sky, Resident Peggy and I were out on a walk with Astronomer Assistants, Ruby and Danny. Well, I was plenty excited and wanted to get back to the observatory and grab my camera so, luckily, and graciously, Resident Astronomer Peggy agreed to keep the assistants busy while I ran (well walked fast really) back and grabbed my tripod and camera with 10mm wide angle lens and managed to take this photo just in time.
|Halo around the moon, 10mm, 8 seconds, 6:11PM (Source: Palmia Observatory)|
Well the cold weather and clouds might have been good for finally photographing the moon with a ring, visible due to ice crystals high in the atmosphere, but it hasn't helped any in finding some clear evenings to make a measurement of the sky brightness. So, it was back to the collection of DVDs from The Great Courses on Radio Astronomy. Two of the 30 minute lectures were a tour of the Green Bank National Radio Observatory and of the large 100 meter radio telescope. It was really neat to see the insides of the telescope and learn how the radio receivers collect the very low power signals gathered by the large dishes. If you don't recall what the large 100 meter scope looks like, take a look at the screenshot below. This dish antenna can receive radio signals from 2.6 mm wavelength to 3 meter wavelength. One of the most important signals is that from neutral hydrogen which generates a 1420 MHz photon when the atomic spin flip occurs. Since most of the universe is made out of hydrogen, being able to map the presence of hydrogen with radio telescopes is a key window on finding out the structure of the universe.
|100 meter Green Bank Radio Telescope (Source: Green Bank Observatory NSF)|
The instructor, Dr. Felix Lockman, explained how this telescope design is called asymmetric in that it is not like the other radio telescopes that we are used to seeing where the dish is symmetric and the receivers or reflector is mounted right in the center of the dish and suspended by three arms attached to the rim of the dish. This old design worked well enough but the new design does away with the loss of signal due to the receiver mounting arms and also does not suffer from any stray ground based signals reflecting off the supporting arms and coming into the telescope receivers as if it had come from outer space.
Anyway, I look forward to reviewing more of the DVD lectures and remember how in the past I had tried to schedule a trip to visit Green Bank and could never quite get it on the schedule. I have tried for three years now to attend the annual meeting of the Society of Amateur Radio Astronomers (SARA) but have not been able to make it because of other plans that crept into the calendar. So, now, for once and all, let's put the next 2018 annual conference, to be held June 10-13, 2018, on the calendar. It should be a lot of fun to meet with other amateur radio astronomers and tour the observatory and countryside in West Virginia. If you are interested check out SARA and conference details at their website: http://radio-astronomy.org/
It's a good thing I put this meeting on the calendar because that time in June is already starting to get booked up, what with the Summer 2018 AAS meeting in Denver just the week before. I don't want to miss out on seeing Green Bank for the third time.
The SARA attendees often look forward to one event that the amateurs always seem to enjoy which is the chance to listen to the universe with the 40 foot dish that is made available for amateur and other public users. SARA members often bring their own receiver designs and have a chance to try them out here as well.
|Amateur Radio Astronomers collecting 1420 MHz signals from the 40 foot dish (Source: SARA photo archives)|
Now I don't think I will be building my own receivers even though I once had quite a bit of interest in software defined radios, which use software rather than filters and modulators and other hardware circuits. But, I did get a bit excited a couple of years ago at the San Diego AAS meeting where I saw for the first time this dish antenna system designed and built for amateur radio astronomers.
|Resident Astronomer dreaming of a dish at the 2016 AAS San Diego meeting (Source: Palmia Observatory)|
When I first saw this telescope designed with amateurs in mind, it was going for about $10k. When I checked online for the current offering at Woodland Hills Telescope, the price is now on sale at $16k. Well, the unit does come with the goto mount and software and low noise amplifiers and signal processing for a couple of bands including 1420 MHz.
|Follow your amateur radio astronomy dream (Source: Woodland Hills Telescope, www.telescopes.net)|
Ok, ok, if you are not going to shell out $16k for this radio telescope, you can sign up for this free internet course on astronomy offered by Duke University. OCA, Moved to the View in the Mountains, David, discovered this course and found it very good. I just signed up and look forward to it also. The level of the course requires some high school algebra (see the instructor and blackboard equations in the photo below). Check out the agenda and details at: https://extend.duke.edu/courses/course-v1:DukeExtend+introastro+2017-2018/about?utm_source=courseraemailist&utm_campaign=new_courseNov17&utm_medium=email
Thanks for that info David!
|Screenshot from Introduction to Astronomy course (Source: Duke University)|
Well after all of this study and more study and watching videos we elected to attend a Cosmos Meetup with the local Orange County Society of the American Institute of Archeology and look up at some astronomical rock paintings. We met up with the rest of the group near Mockingbird Canyon in Riverside, CA, and toured the site. About 15 of us showed up with our AIA host, Steve, and our very knowledgeable guide, Stephen, who lead this group of archeological adventurers over a little stream and at least one centipede, to see some historical rock paintings still available and accessible in this urban environment.
The most significant view was going through a rock tunnel, formed by collapsed boulders, where the rock art was mostly on the ceiling, which was visible as we crawled through the tunnel on all fours. This site was apparently used for initiation of young native peoples living in the area at that time. The paintings show supposed images of the Milky Way, yeah at a time when you could actually see it in OC, and I certainly could see how crawling through the tunnel could be experienced as being born and opening out into the wider world, surrounded by the stars above.
|Astronomical rock paintings on ceiling while still crawling in the tunnel (Source: Palmia Observatory)|
The tunnel was narrow enough and low enough that we had to crawl and not stand up and I managed to take a few photos with my IPhone. It would have been nice to take a little more time and make sure I captured all of the rock paintings but, honestly, I was kind of glad to get out of the tight space. When I got to the point in the tunnel when I could mostly standup, I turned around to take another photo of the ceiling, just as Resident Astronomer Peggy was making her entrance.
|My final ceiling view in the rock tunnel as Resident Astronomer Peggy crawls in (Source: Palmia Observatory)|
I'm not sure I see the Milky Way in the paintings, but it was fun and exciting to be able to still see these old paintings without them being vandalized or destroyed by the weather. Also we will be in Portugal next year on a river cruise and are still undecided if we shouldn't extend our visit there and see so of the much older, prehistoric cave paintings found there in the border area between France and Spain. It's going to take a lot more preparation and study and listening to the experts just to understand what we see and how we should interpret these paintings. Hmm, maybe its just like in astronomy how we have to learn how to interpret the message contained in the light curve or spectra or image that we see in our telescopes?
Until next time,